Polyurethane polymers can be used as a coating for a variety of applications. For example, they can be used as a coating for coated substrates, such as a coated transparency for an aircraft. Aircraft transparencies (e.g., canopies), and particularly stealth aircraft canopies, preferably include a low resistance (i.e., high electrical conductivity) layer (or layers) to prevent or reduce the buildup of static charge and to provide radar attenuation. Static charge can buildup on a canopy as the result of precipitation static and/or lightning strikes, and may interfere with various functions of the aircraft. By including a low resistance layer (or layers), an aircraft canopy can drain or dissipate static electricity and thereby prevent or reduce the buildup of static charge on the canopy. The low resistance layer (or layers) may be coated with a high resistance coating (e.g., a polyurethane antistatic topcoat), so long as static charge can be transferred through the organic topcoat into the low resistance layer (or layers).
Modern jet aircraft canopies, such as F-22 stealth fighter canopies, are typically made of polymeric materials. Such materials are desirable because of their light weight, high strength, and ease of shaping. Most polymeric materials, however, do not meet the requirements for stealth aircraft, such as low sheet resistance and the ability to withstand extreme weather conditions. As a result, coatings (e.g., organic and inorganic coatings) are employed to impart high electrical conductivity and other characteristics to the canopy.